This invention relates to ground coils for a magnetically levitated railway and, more particularly, to a ground-propulsion special-purpose electromagnetic circuit secured to the side walls of a guideway.
An example of the prior art in the technical field to which the present invention appertains will now be described.
As shown in FIG. 2, four unit coils 1.about.4 for levitation and guidance are arranged in an identical cross section in the traveling direction of a vehicle. The coils 1.about.4 are connected by null-flux connectors 5 for levitation in such a manner that voltages generated by magnetic flux interlinking with the upper and lower coils when the vehicle passes by cancel each other out, thereby producing a levitating force. Furthermore, null-flux connecting lines 6 and 7 for guidance are provided in such a manner that induced voltages generated by flux interlinking with mutually opposing unit coils, namely coils 1 and 3 and coils 2 and 4, will cancel each other.
A special-purpose coil 9 exclusively for propulsion is supplied with electric power from an external power supply 8. The coil 9, which is placed entirely independently of the above-mentioned coils for levitation and guidance, is so arranged as to propel the vehicle in cooperation with superconducting magnets (superconducting coils, which are not shown) mounted on the vehicle.
This system has already been disclosed by the applicant in U.S. Pat. No. 4,913,059.
As shown in FIG. 1, a plurality of the special-purpose coils 9 for propulsion branch from feeder lines U, V, W and are serially connected to phases U, V, W, respectively, via a switch SW. Further, the U, V and W phases are interconnected in a terminating unit TM and connected to a neutral line N. In other words, the phases are Y-connected to construct one section.
In FIGS. 3 and 4, a ground-coil fixing panel 11 is provided on a side wall 10 of a guideway. A first propulsion coil 12 having a lead-wire terminal 13 for connecting coils, a second propulsion coil 14 having a lead-wire terminal 15 for connecting coils and a levitation-guidance coil 16 molded from resin are mounted on the ground-coil fixing panel 11.
As shown in FIG. 4, the ground coils for the magnetically levitated railway according to the prior art described above are such that the independently wound first propulsion coil 12 having the lead-wire terminal 13 for connecting coils and the second propulsion coil 14 having the lead-wire terminal 15 for connecting coils are placed to correspond to each of the levitation-guidance coils. Since a high voltage is impressed upon the propulsion coils 12, 14, the terminals are costly and difficulty is encountered in terms of reliability.
The number of turns in a propulsion coil is decided by the number of cars of the vehicle connected together, the required acceleration, etc. The smaller the overall length of the interconnected cars, that is, the smaller the number of superconducting magnets, and the higher the acceleration, the greater the number of turns. In the case of the Miyazaki Test Track, the overall length of the interconnected cars is small and therefore the propulsion coils have 32 turns. In the case of the Yamanashi Test Line, the overall length of the interconnected cars is greater than that of the Miyazaki Test Track and therefore the propulsion coils have seven to ten turns. Since the overall length in future commercial lines for high-volume transportation will naturally be great, it is predicted that the number of turns will be small.
Accordingly, an object of the present invention is to adopt a system in which, rather than relying upon the individual propulsion coils of the prior art, cables are wound on side walls of a guideway in wave-like fashion to form electromagnetic winding, whereby one turn of a coil is arranged so as to correspond to one cable (i.e., one vertical side thereof).
Thus, an object of the invention is to provide a ground-propulsion special-purpose electromagnetic circuit for a magnetically levitated railway, as well as a method of laying the circuit, in which the number of lead-wire terminals of the propulsion coils can be greatly reduced, cost lowered and reliability improved.